Conventionally, a press brake is used a lot for bending a plate-shaped workpiece, and when a worked product is manufactured, the bending which provides highly accurate bending angle and flange dimension of a workpiece is strongly desired. For this reason, a bending apparatus which has an angle detecting device for measuring a bending angle of a workpiece instantly and accurately is required.
The above-mentioned angle detecting device 301 is disclosed in Japanese Patent Application Laid-Open No. 6-238343 (1994), and it is, as shown in FIG. 1, provided with a measuring disk 303 having a shape of a flat semicircular disk whose measuring member has a smaller thickness than a width of its plane. The measuring disk 303 is mounted to a disk supporting section 309 of a V groove portion 307 of a mold die 305 so as to rotate through a limited angle.
The die 305 is provided with a lateral slot 211 on one surface of the V groove portion 307 so that the measuring disk 303 can pass through the slot 211, and a center portion 315 of a linear edge portion 313 of the measuring disk 303 can move between a position inside a slot 311 in a vicinity of the V groove portion 307 and a position outside the slot 311.
The disk supporting section 309 which bears the measuring disk 303 is positioned so as to come in contact with a workpiece W bent by the linear edge portion 313 of the measuring disk 303. The disk supporting section 309 is provided with means for detecting an angle position of the measuring disk 303 using, for example, electric, optical or hydrodynamic means, and means for supplying the measured signal. Therefore, the instant bending angle of the workpiece W is detected by the angle position of the measuring disk 303.
Incidentally, in the conventional art, since the measuring disk 303 is provided to the V groove portion 307 of the die 305, the die 305 has the slot 311 for receiving the measuring disk 303. For this reason, the arrangement of the measuring disk 303 is necessary for every replacement of molds according to mold conditions which differ due to workpiece shapes and shape of V grooves different due to plate thickness and the like.
In addition, since one measuring disk 303 exists on one surface of the V groove portion 307 of the die 305, the bending angle detecting device 301 should be set in at least two places in order to measure the bending angle of the workpiece W.
Further, since the measuring disk 303 extends upward from the upper surface of the die 305, when the workpiece W is carried in from the lateral direction so as to slide on the upper surface of the die 305, there arises a problem that interference between the workpiece W and the measuring disk 303 occurs.
In addition, since the measuring disks 303 operate individually so as to follow the sliding of the workpiece W, there arises a problem that its bending angle detecting portion becomes complicated.
Meanwhile, another conventional art has the following problem.
Namely, a press bake is used a lot for bending a plate-shaped workpiece, and highly accurate bending is strongly desired for manufacturing a worked product with high quality. Incidentally, the high accuracy is accuracy of the bending angle and the flange dimension of the bent workpiece. In actual bending, an upper table to which a punch is mounted, for example, is reciprocated, and a workpiece is bent by a cooperation of the punch and the die mounted to a lower table. Here, an angle sensor for measuring the bending angle of a workpiece is mounted to the press brake in a longitudinal direction of the die.
When the bending is carried out, the position of the angle sensor is read by an operator through a scale stuck to the upper table, and the operator inputs the read value into a control device using a ten key.
In addition, the press brake of another example is provided with the angle sensor in the longitudinal direction of the mold movably, and when a workpiece is bent, the angle sensor is automatically moved by the control device so as to measure the bending angle of the workpiece automatically.
In the former one of the conventional arts, when the operator reads the position of the angle sensor mounted to the press brake through the scale of the upper table, the operator reads it by mm unit from the reference position at the left end and memorizes it and moves to the control device so as to input the memorized and read numerical value using the ten key. For this reason, there arises a problem that of troublesome input operation and misinput. Here, since the angle sensor is provided in, for example, three places maximally, the above operation should be repeated three times, and thus this is a troublesome operation for the operator.
In the latter art, although the angle sensor is moved automatically by the control device, in the case where a bending angle cannot be measured because a hole or the like exists in the automatically determined place, there arises a problem that the position of the angle sensor should be input by using the ten key and the provided position of the angle sensor should be adjusted.
The present invention is devised in order to solve the above problems, and its first object is to provide a bending apparatus, which has a bending angle detecting device which does not depend on the mold conditions such as a groove width of the die and R of a groove shoulder portion and in which a disk for measuring a bending angle of a workpiece retreats below the die upper surface so as not to interfere with the workpiece when the workpiece is carried in and which follows according to the bending angle so as to come in contact with a linear portion of the workpiece while avoiding the bent R portion at the time of detecting the bending angle of the workpiece, and which is capable of detecting the bending angle accurately using at least one bending angle detecting device and bending the workpiece.
The second object of the present invention is to provide a bending method and an apparatus thereof which are capable of detecting a position of an angle sensor without input using keys by an operator so as to eliminate an arrangement operation and misinput and detecting a bending angle of a workpiece at real time so as to bend the workpiece accurately.